[PATCH] Remove f-strings from DAP

[Tom Tromey <tromey@adacore.com>]

Kévin pointed out that gdb claims a minimum Python version of 3.2, but
the DAP code uses f-strings, which were added in 3.6.

This patch removes the uses of f-strings from the DAP code.  I can't
test an older version of Python, but I did confirm that this still
works with the version I have.
---
 gdb/python/lib/gdb/dap/evaluate.py | 2 +-
 gdb/python/lib/gdb/dap/io.py       | 2 +-
 gdb/python/lib/gdb/dap/launch.py   | 2 +-
 gdb/python/lib/gdb/dap/state.py    | 2 +-
 4 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/gdb/python/lib/gdb/dap/evaluate.py b/gdb/python/lib/gdb/dap/evaluate.py
index fffd255417b..7c4fee4f84b 100644
--- a/gdb/python/lib/gdb/dap/evaluate.py
+++ b/gdb/python/lib/gdb/dap/evaluate.py
@@ -62,7 +62,7 @@ def eval_request(*, expression, frameId=None, context="variables", **args):
     elif context == "repl":
         return send_gdb_with_response(lambda: _repl(expression, frameId))
     else:
-        raise Exception(f'unknown evaluate context "{context}"')
+        raise Exception("unknown evaluate context " + context)
 
 
 @in_gdb_thread
diff --git a/gdb/python/lib/gdb/dap/io.py b/gdb/python/lib/gdb/dap/io.py
index 7cec7b032e3..2f3a2351925 100644
--- a/gdb/python/lib/gdb/dap/io.py
+++ b/gdb/python/lib/gdb/dap/io.py
@@ -60,7 +60,7 @@ def start_json_writer(stream, queue):
             seq = seq + 1
             encoded = json.dumps(obj)
             body_bytes = encoded.encode("utf-8")
-            header = f"Content-Length: {len(body_bytes)}\r\n\r\n"
+            header = "Content-Length: " + str(len(body_bytes)) + "\r\n\r\n"
             header_bytes = header.encode("ASCII")
             stream.write(header_bytes)
             stream.write(body_bytes)
diff --git a/gdb/python/lib/gdb/dap/launch.py b/gdb/python/lib/gdb/dap/launch.py
index 21499a339e1..428fd811471 100644
--- a/gdb/python/lib/gdb/dap/launch.py
+++ b/gdb/python/lib/gdb/dap/launch.py
@@ -40,7 +40,7 @@ def launch(*, program=None, args=[], env=None, **extra):
     if program is not None:
         global _program
         _program = program
-        send_gdb(f"file {_program}")
+        send_gdb("file " + _program)
     if len(args) > 0 or env is not None:
         send_gdb(lambda: _set_args_env(args, env))
 
diff --git a/gdb/python/lib/gdb/dap/state.py b/gdb/python/lib/gdb/dap/state.py
index caf654aaf07..f4f81d2afa0 100644
--- a/gdb/python/lib/gdb/dap/state.py
+++ b/gdb/python/lib/gdb/dap/state.py
@@ -22,4 +22,4 @@ def set_thread(thread_id):
     if thread_id == 0:
         log("+++ Thread == 0 +++")
     else:
-        exec_and_log(f"thread {thread_id}")
+        exec_and_log("thread " + str(thread_id))
-- 
2.40.0